A standard motor-vehicle sliding door moves on tracks between a closed position and an open position. It is now standard to provide a drive for power-assisted and even remote operation of this door, which under the best of circumstances can be difficult to manipulate.
In a standard arrangement a pair of cable sections, which may be separate or parts of a common cable, each have one end anchored on the door and an opposite end anchored on a respective drum. The drums are coaxially mounted on a common drive pin and are biased in angularly opposite directions by a spring connected between them to keep the cable sections taut. A drive gear rotated by a reversible electrical motor can engage one or the other of the coaxial drums, depending on whether the door is to be opened or closed, to rotate the two drums, paying the cable off one of them and winding it up on the other.
To preserve the cable each of the drums is formed with a helical groove intended to receive the respective cable section when it is wound thereon. It is important that the cable wind up smoothly, without turns one atop the other, so that the cable itself does not chafe and in order to maintain the assembly as compact as possible.
The problem with this arrangement is that the drums are fairly expensive to manufacture, mainly due to formation of the helical cable-seat groove. In addition the cable is pulled at an angle at least toward the end of a windup operation, so it is fairly common for the cable to jump out of its groove and ride up on previously laid turns, causing a chafing problem and possibly leading to binding of the drum due to its increased diameter.